Automotive seats assemblies and restraint systems have long been used with active systems, such as airbags, in an attempt to minimize the risk of serious injury to vehicle occupants involved in a crash. These crashes include frontal, rear, side, rollover and combinations thereof that impart forces on the occupant in numerous directions. The occupants of these vehicles vary in size, weight, and height, and girth. Additionally, seat adjustments create further complexities of occupant positioning relative to the adjacent structures. The combinations of impact speed, impact type, occupant size, and occupant position create a nearly infinite number of impact scenarios which could never practically be tested for. Government and Insurance agencies have created test protocols to cover the most likely impact scenarios. However, serious injuries and fatalities still occur.
Seat manufacturers are continuously challenged to reduce the profile of the seat in an effort to increase the volume of space available for the occupant. As these seat assemblies decrease in thickness, less stroke is provided for impact management in the assembly, thereby necessitating higher efficiency in energy absorbing performance so that more energy can be absorbed in less space. Large foam buns have traditionally been used for both comfort and energy management. However, foam has proven to be less than ideal as an energy absorber due to its slow ramp up in load and poor crush efficiency. Furthermore, the foam density one would choose based on comfort characteristics is far too soft for energy management during a vehicle crash. Therefore a second stage energy absorber is desirable that has improved energy management properties and crush efficiency over the prior art with the resiliency to withstand every day operating loads that are less than one would experience in a vehicle crash.
Automotive interior systems, including vehicle seats, seat backs, consoles, door trim, pillar trim and other interior panels, are designed to withstand the day to day abuse they are likely to see in practical use. The driver's seat in particular, must be capable of withstanding tens of thousands of ingresses and egresses in conjunction with supporting the driver during the operation of the vehicle. Fabric or leather covered polyurethane (PU) foam has been traditionally been used in conjunction with a metal seat frame supporting structure to satisfy both comfort and crash criteria. Mechanical adjusters, heating, cooling, and airbags are also integrated into the seat assembly to enhance comfort and crash characteristics.
Efforts made with PU foam in particular to enhance the performance of the foam system for both comfort and crash include two main groups. Group one consists of using a reactive “dual” density approach where one density is used for comfort and one or more densities are molded for energy absorption following a crash. These may utilize not only changes in density but chemistry as well to obtain desired performance characteristics or both in the seat bun and the seat back. Group two consists of insert molding another foam component, made of EPP foam or some other foam type, and foaming the comfort PU foam around these energy§ absorbing foam components. Group two provides more flexibility to optimize the system crash performance and manage the loads the occupant experiences in a crash. These include changing the shape, density, chemistry, and position of these energy absorbing materials within the foam bun. However, there is still a need to address the inherent inefficiency of prior art foam energy absorbers.
Interior trim parts often cover structural members that are rigid with blunt edges. These structural members may be in the vicinity of the occupant during daily use as well as in a crash event. Contact with these members in a crash could result in serious injury. Therefore, it is desirable to have an energy absorbing structure which would cushion the occupant during an impact, mitigate some of the impacting forces and reduce the risk of serious injury. Ideally, this energy absorbing structure would be engineered in such a way that it would be able to adapt to the shapes of various structural members one would like to protect. In this way, one tool could produce a product that could be applied to a variety of structural members.